Uncoated cutting tool using brazed-in superhard blank

ABSTRACT

An uncoated cutting tool that comprises a body containing a pocket. A polycrystalline cubic boron nitride blank has a cutting tip. The blank is brazed into the pocket using a braze alloy whereby there is a braze joint between the body and the polycrystalline cubic boron nitride blank. The braze alloy has a liquidus temperature of at least about 900 degrees Centigrade wherein the braze alloy is selected from the group comprising a nickel-gold braze alloy containing nickel and gold, a copper-gold braze alloy containing copper and gold, a silver-titanium braze alloy containing silver and titanium, and a silver-palladium braze alloy containing silver and palladium.

REFERENCE TO EARLIER PATENT APPLICATION

This patent application is a divisional patent application of co-pendingU.S. patent application Ser. No. 10/463,467 filed on Jun. 17, 2003.

BACKGROUND OF THE INVENTION

The present invention relates to a cutting tool that uses a superhardblank. More specifically, the present invention pertains to an uncoatedcutting tool that uses a brazed-in polycrystalline cubic boron nitride(PcBN) blank or, in the alternative, a brazed-in polycrystalline diamond(PCD) blank.

Heretofore, there have been known cutting tools that use a superhardblank as the cutting element that provides a cutting edge. These cuttingtools comprise a cutting tool body that contains a notch or pocket. Thesuperhard blank is brazed into the notch or pocket using a braze alloyso that a braze joint is formed between the superhard blank and thecutting tool body.

In one alternative, the superhard blank comprises a support (e.g.tungsten carbide) on which there is a layer of superhard material (e.g.polycrystalline cubic boron nitride or polycrystalline diamond). Inanother alternative, the superhard blank comprises a single piece ofsuperhard material (e.g. polycrystalline cubic boron nitride orpolycrystalline diamond). During the material removal operation, thesuperhard layer defines a cutting edge that comes into contact with theworkpiece material to remove workpiece material so as to function as acutting element.

During the material removal operation there is generated heat (andsometimes considerable) heat at the point of contact between the cuttingedge of the superhard layer and the workpiece material. This isespecially the case when the cutting tool uses a PcBN blank. Highercutting temperatures also exist when using superhard blanks to removematerial from workpiece material that is hard such as, for example, a D3tool steel (AISI D3). Such a material has a hardness on the order ofRockwell C 60 wherein the quenched hardness can range between about 64to about 66 Rockwell C and the tempered hardness can range between about54 and about 61 Rockwell C. Higher cutting temperatures also exist incertain material removal operations such as threading, grooving, partingand some particularly difficult turning and milling operations.

Because of the generation of excessive heat, the use of cutting toolswith a brazed-in superhard blank have experienced the drawback of thedebrazing of the superhard blank from the cutting tool body. In otherwords, the heat generated at the point of contact between the superhardblank and the workpiece material passes through the superhard blank soas to cause the temperature at the braze joint to reach such a levelthat the braze alloy melts (or softens) thereby reducing the shearstrength of the braze joint. A reduction in the shear strength of thebraze joint weakens the braze joint so that the cutting forces exertedon the superhard blank can detach the superhard blank from the cuttingtool body.

Dry cutting processes such as removing material by machining fromcarbon:carbon composite materials, abrasive-reinforced polymericmaterials, and various types of wood materials through the use ofcutting tools using a brazed-in PCD blank can also generate highercutting temperatures. As mentioned earlier, these higher cuttingtemperatures result in a higher temperature at the braze joint. Thesehigher temperatures at the braze joint can result in a softening ormelting of the braze alloy thereby reducing the shear strength so as tocause the PCD blank to become detached or separated from the cuttingtool body under the influence of the cutting forces exerted on the PCDblank.

The degree of the cutting forces exerted on the cutting tools taken inlight of the cutting temperature, the temperature at the braze joint,the liquidus temperature of the braze alloy, and the shear strength ofthe braze alloy appear to influence the ability of the superhard blankto be retained in the pocket of the cutting tool. When the temperatureat the braze joint reaches a certain level, there begins a reduction inthe shear strength of the braze joint. When the shear strength of thebraze joint is less than necessary to maintain its integrity against thecutting forces exerted on the superhard blank, the superhard blankbecomes detached from the cutting tool body. As one can appreciate, thepremature (or catastrophic) separation or detachment of the superhardblank from the cutting tool body is an undesirable result.

It would thus be desirable to provide an uncoated cutting tool that usesa brazed-in superhard blank as the cutting element that presents acutting edge wherein the braze joint between the cutting tool body andthe superhard blank is able to withstand the heat generated during thematerial removal operation.

It would also be desirable to provide an uncoated cutting tool that usesa brazed-in superhard blank as the cutting element that presents acutting edge wherein the braze joint between the cutting tool body andthe superhard blank is able to withstand the heat generated during thematerial removal operation through the use of braze alloys that maintainan adequate shear strength at the temperatures that exist at the brazejoint during the material removal operation (i.e., high temperaturebraze alloys) so as to maintain the integrity of the braze joint.

It would further be desirable to provide an uncoated cutting tool thatuses a brazed-in superhard blank as the cutting element that presents acutting edge wherein the braze joint between the cutting tool body andthe superhard blank is able to withstand the heat generated during thematerial removal operation through the use of high temperature brazealloys along with the geometry and design of the superhard blank so asto reduce the exposure of the braze joint to excessive temperatures sothat the integrity of the brazed joint is maintained during the materialremoval operation.

Finally, it would be desirable to provide an uncoated cutting tool thatuses a brazed-in superhard blank as the cutting element that presents acutting edge wherein the braze joint between the cutting tool body andthe superhard blank is able to withstand the heat generated during thematerial removal operation through the geometry and design of thesuperhard blank so as to reduce the exposure of the braze joint toexcessive temperatures so that the integrity of the braze joint ismaintained during the material removal operation.

SUMMARY OF THE INVENTION

In one form thereof, the invention is an uncoated cutting tool thatincludes a body containing a pocket. A polycrystalline cubic boronnitride blank is brazed into the pocket using a braze alloy. The brazealloy has a liquidus temperature of at least about 900 degreesCentigrade.

In another form thereof, the invention is an uncoated cutting tool thatcomprises a body containing a pocket. A polycrystalline cubic boronnitride blank is brazed into the pocket using a braze alloy. The brazealloy has a liquidus temperature of at least about 940 degreesCentigrade. The braze alloy comprises gold and nickel, and the goldbeing present in an amount ranging between about 65 weight percent andabout 90 weight percent, and the nickel being present in an amountranging between about 15 weight percent and about 25 weight percent.

In yet another form thereof, the invention is an uncoated cutting toolthat comprises a body that contains a pocket. A polycrystalline cubicboron nitride blank is brazed into the pocket using a braze alloy. Thebraze alloy has a liquidus temperature of at least about 900 degreesCentigrade. The braze alloy comprises silver, copper and titanium, andthe silver being present in an amount ranging between about 65 weightpercent and about 75 weight percent, the copper being present in anamount ranging between about 20 weight percent and about 30 weightpercent, and the titanium being present in an amount ranging betweenabout 2.5 weight percent and about 6.5 weight percent.

In still another form thereof, the invention is an uncoated cutting toolfor removing material from a workpiece in a material removal operationwherein the uncoated cutting tool engages the workpiece at a selecteddepth of cut. The uncoated cutting tool comprises a body that contains apocket. A polycrystalline cubic boron nitride blank has a rake surface,a cutting edge and a leg that extends away from the cutting edge. Theblank is brazed into the pocket using a braze alloy whereby there is abraze joint between the body and the polycrystalline cubic boron nitrideblank. The braze alloy has a liquidus temperature of at least about 900degrees Centigrade wherein the braze alloy is selected from the groupcomprising a nickel-gold braze alloy containing nickel and gold, acopper-gold braze alloy containing copper and gold, a gold-copper-nickelbraze alloy contains gold and copper and nickel, asilver-titanium-copper braze alloy containing silver and titanium andcopper, and a silver-palladium braze alloy containing silver andpalladium. The braze joint is located a distance away from the rakesurface of the polycrystalline cubic boron nitride blank ranging betweenabout 1.5 millimeters and about 4.9 millimeters and the leg having alength that is at least about 1.7 times as great as the depth of cut.

In still another form thereof, the invention is an uncoated cutting toolfor removing material from a workpiece in a material removal operationwherein the uncoated cutting tool comprises a body that contains apocket. A superhard blank has a rake surface and a cutting edge whereinthe blank is brazed into the pocket using a braze alloy whereby there isa braze joint between the body and the blank. The braze alloy has aliquidus temperature. The superhard blank engages the workpiece duringthe material removal operation so that cutting forces are exerted on thesuperhard blank and heat is generated at the cutting of the superhardblank. The braze joint is located a selected distance away from thecutting edge so that the temperature at the braze joint is less than theliquidus temperature of the braze alloy whereby the braze joint hassufficient shear strength to retain the superhard blank in the pocketduring the material removal operation.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a brief description of the drawings that form a part ofthis patent application:

FIG. 1 is an isometric view of one embodiment of an uncoated cuttingtool that comprises a body with a pocket or notch and an uncoatedpolycrystalline cubic boron nitride insert brazed therein;

FIG. 2 is a cross-section view of the cutting tool of FIG. 1 taken alongsection line 2-2 of FIG. 1;

FIG. 3 is an isometric view of another embodiment of an uncoated cuttingtool (i.e., a threading tool) that contains a pocket and an uncoatedpolycrystalline cubic boron nitride blank brazed therein wherein theblank comprises a layer of polycrystalline cubic boron nitride and alayer of tungsten carbide;

FIG. 4 is a top schematic view of a portion of an uncoated threadingtool showing selected dimensions of the polycrystalline cubic boronnitride blank;

FIG. 5 is a side schematic view of the uncoated cutting tool of FIG. 4showing selected dimensions of the polycrystalline cubic boron nitrideblank;

FIG. 5A is a side schematic view of the uncoated cutting tool of FIG. 4that shows thermal gradients therein as would occur during a materialremoval operation

FIG. 6 is a cross-sectional view of a corner of an uncoated threadingtool wherein the PcBN blank comprises one piece of PcBN material;

FIG. 7 is an isomeric view of an uncoated grooving tool that presents aTOP NOTCH® (TOP NOTCH® is a registered trademark of Kennametal Inc. ofLatrobe, Pa. USA) style of geometry; and

FIG. 8 is an isomeric view of an uncoated threading tool that presents aTOP NOTCH® (TOP NOTCH® is a registered trademark of Kennametal Inc. ofLatrobe, Pa. USA) style of geometry.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, FIGS. 1 and 2 illustrate one embodiment ofthe uncoated cutting tool generally designated as cutting tool 20.Cutting tool 20 has a body 22 that contains a notch or pocket 24. Thebody 22 can be made from a number of materials, but one preferredmaterial is cobalt cemented tungsten carbide. The notch 24 is located atone corner of the body 22, but it should be appreciated that the notchcould be at opposite corners or at all four corners of the body 22.

A polycrystalline cubic boron nitride (PcBN) blank 25 is brazed to thebody 22 at the notch 24. PcBN blank 25 comprises a cobalt tungstencarbide support 26 on which there is a layer of polycrystalline cubicboron nitride 27. Although specific compositions of PcBN will be setforth hereinafter, the typical PcBN material is a mixture of cubic boronnitride and another material such as, for example, titanium carbide orcobalt or some other suitable binder material. A braze joint 28 is atthe juncture between the body 22 and the PcBN blank 25. As mentionedabove, one objective of the invention is to provide an uncoated cuttingtool that uses a brazed-in superhard blank wherein the braze jointbetween the cutting tool body and the PcBN blank is able to withstandthe heat generated during the material removal operation. One way toaccomplish this goal is to use a high temperature braze alloy. In thisregard, one acceptable braze alloy for this application is a hightemperature braze alloy in which the liquidus temperature (i.e., thelowest temperature at which the alloy is completely liquid) is at leastabout 900 degrees Centigrade. Braze alloys such as those identified inTable 1 hereof are suitable high temperature braze alloys.

Referring to FIG. 3, there is shown another embodiment of an uncoatedcutting tool generally designated as 40. Cutting tool 40 is one exampleof a threading tool. Cutting tool 40 includes a body 42 that contains apocket 44 and an aperture 45. As discussed above with respect to thebody 22 of cutting tool 20, the body 42 may be made from a number ofmaterials including cobalt cemented tungsten carbide. An uncoatedpolycrystalline cubic boron nitride blank 46 is brazed within the pocket44. The PcBN blank 46 comprises a PcBN layer 48 and a cemented carbide(e.g., cobalt cemented tungsten carbide) support 50. The PcBN blank 46has a rake surface 52 and a flank surface 54. There is a cutting edge 56at the intersection of the rake surface 52 and the flank surface 54.

Like for the cutting tool 20 of FIGS. 1 and 2, the composition of thePcBN layer may vary depending upon the specific application. KD050 isone specific composition for the PcBN layer wherein this compositioncomprises about 50 volume percent cubic boron nitride and about 50volume percent titanium carbide. KD120 is another specific compositionfor the PcBN layer wherein this composition comprises about 88 volumepercent cubic boron nitride and about 12 volume percent cobalt. Thesupport 50 may also comprise any one of a variety of compositionsdepending upon the application. As mentioned above, one common materialfor the support 50 is cobalt cemented tungsten carbide.

Referring to FIGS. 4 and 5, there is shown in schematic form thearrangement of a PcBN blank 60 brazed into the pocket 62 of a body 64for a threading tool generally designated as 66. The PcBN blank 60comprises a layer of PcBN 68 and a cobalt cemented tungsten carbidesupport 70. There is a braze joint 63 between the PcBN blank 60 and thesurfaces of the tool body 64 that define the pocket 62. The PcBN blank60 has a rake surface 71 and a flank surface 72. A cutting edge 73 is atthe intersection of the rake surface 71 and the flank surface 72.

As mentioned above, an objective of the present invention is to providean uncoated cutting tool that has a brazed-in superhard (e.g., PcBN)blank wherein the braze joint between the cutting tool body and the PcBNblank is able to withstand the heat generated during the materialremoval operation. A way to optimize the ability of the braze joint towithstand the temperatures that exist at the braze joint during acutting operation is to locate the braze joint an optimum distance awayfrom the point of contact between the PcBN blank (i.e., the cuttingedge) and the workpiece material.

The dimensions of the PcBN blank determine the distance between thepoint of contact and the braze joint. In the case of a superhard blankthat comprises a PcBN layer on a cobalt cemented tungsten carbidesupport, the selection of these dimensions is based on balancing thecost of increasing the size of the layer of PcBN or increasing the sizeof the support (or a combination of increasing the size of the layer ofPcBN and the size of the support) against the extent of thermalprotection for the braze joint due to the distance between the point ofcontact and the braze joint. In the case of a superhard blank that isone piece of PcBN, the size (and hence the cost) of the PcBN piece isbalanced against the extent of thermal protection of the braze joint dueto the distance between the point of contact and the braze joint.

FIG. 5A is a schematic view that shows thermal gradient lines T_(max)and T₁ through T₅ for the cutting tool as would occur during a materialremoval operation. The maximum temperature is (T_(max)) is at the pointof contact between the cutting edge of the PcBN blank and the workpiecematerial. The temperature gradient lines T₁, T₂, T₃, T₄, and T₅represent five different temperatures at various distances away from thepoint of contact. As one can appreciate, the temperature decreases asone moves farther away from the point of contact. The temperaturegradient has the following relationship: T₁>T₂>T₃>T₄>T₅.

The braze joint 63 comprises the joint between the PcBN blank and thepocket contained in the cutting tool body wherein the braze joint hastwo principal portions. One portion is between the PcBN blank and theseating (or horizontal in FIG. 5A) surface of the pocket and the otherportion is between the PcBN blank and the backing (or vertical on FIG.5A) surface. These temperature gradient lines show that the braze joint63 is exposed to the higher temperatures at a location near the point ofcontact and that the temperature decreases as one moves farther awayfrom the point of contact. By selecting certain dimensions of the PcBNblank that impact upon the location of the braze joint relative to thecutting edge, one can select the temperature that exists at the brazejoint or at least provide some degree of thermal protection for thebraze joint. In the case of a superhard blank that comprises a Supportand a PcBN layer, the thickness of the support is typically increasedsince it is the least expensive component of these two components of thesuperhard blank. The extent to which the thickness of the support isincreased depends upon the cutting temperatures and the properties(e.g., the liquidus temperature and the shear strength) of theparticular braze alloy. The thickness of the Support would be sufficientso that the temperature that exists at the braze joint, which in FIG. 5Awould be about T₅, would be less than the liquidus temperature of thebraze alloy and so that the braze alloy would possess sufficient shearstrength so as to maintain the integrity of the braze joint so as tothereby retain the PcBN blank to the cutting tool body against thecutting forces that would be exerted on the PcBN blank.

In one embodiment as illustrated in FIGS. 4 and 5 the length “a” of thePcBN blank 60 is 0.190 inches (4.82 millimeters); the thickness “d” ofthe PcBN layer 68 is 0.030 inches (0.76 millimeters); the thickness “c”of the support 70 is 0.160 inches (4.1 millimeters); and the overallthickness “b” of the PcBN blank 60 is 0.190 inches (4.83 millimeters).The leg length of the superhard blank is dimension “e”, and it equalsabout 0.220 inches (5.59 millimeters).

Set forth below in Table 1 are typical braze alloys useful for thebrazing of the polycrystalline cubic boron nitride blanks to the body ofthe cutting tool.

TABLE 1 Examples of Useful High Temperature Braze Alloys Solidus MeltingLiquidus (De- Point Composition (Degrees grees (Degrees Shear Braze(weight Centi- Centi- Centi- Strength Alloy percent) grade) grade)grade) (pounds) Gold-   50% Au 969 954 954 13,752 Copper   50% Cu Gold-  35% Au 1028 973 973 12,844 Copper-   62% Cu Nickel   3% Ni Gold- 37.5%Au 1015 940 940 13,023 Copper 62.5% Cu Bau-4   82% Au 948 948 948 21,686Gold-Nickel   18% Ni Bau-6 Gold-   70% Au 1045 1006 1006 26,670 Nickel-  22% Ni Palladium   8% Pd Silver- 68.8% Ag 900 750 750 Not Titanium26.7% Cu Measured  4.5% Ti Silver-   95% Ag 995 970 970 Not Palladium  5% Pd MeasuredIn the Table 1 above, the shear strength is reported in pounds and isthe result of a test in which a one-half inch square carbide is brazedto a carbide member and the braze joint between these carbide members(i.e., a carbide-to-carbide braze joint) is placed in pure shear. Thebraze joint is continually loaded until failure and the result is givenin the pounds at which the braze joint failed.

Cutting tools have been made using the above braze alloys wherein thePcBN layer of the blank comprises either the KD050 composition or theKD120 composition. In testing applicants have found that these cuttingtools that have the brazed-in PcBN blank that use the high temperaturebraze alloys have shown improved performance results as compared tocutting tools that have brazed-in PcBN blanks that used a lowtemperature braze alloy (i.e., an alloy that has a liquidus equal to orless than 675 degrees (Centigrade). Along this line, applicants havefound that the results are very good in the hard turning of hard steelssuch as AISI D3 tool steel that has a hardness in the range of about 60Rockwell C wherein the quenched hardness can range between about 64 toabout 66 Rockwell C and the tempered hardness can range between about 54and about 61 Rockwell C.

As will become apparent from the discussion hereinafter, in someinstances, applicants also contemplate using lower temperature brazealloys that have a liquidus temperature in the range of about 600degrees Centigrade to about 650 degrees Centigrade (or about 750 degreesCentigrade) in conjunction with a cutting tool using a brazed-insuperhard blank wherein the superhard blank has a geometry so that thebraze joint between the cutting tool body and the superhard blank is notexposed to excessive temperatures during the material removal operation.As mentioned earlier, the dimensions of the PcBN blank determine thedistance between the point of contact with the workpiece material andthe braze joint so as to provide a degree of thermal protection for thebraze joint. The extent to which the thickness of the support (or thePcBN layer) is increased depends upon the cutting temperatures as wellas the properties of the particular braze alloy. These dimensions shouldbe selected so that the temperature that exists at the braze joint wouldbe less than the liquidus temperature of the braze alloy so that thebraze alloy would possess sufficient shear strength so as to maintainthe integrity of the braze joint thereby retaining the PcBN blank to thecutting tool body against the cutting forces that would be exerted onthe PcBN blank. Table 2 below sets forth the properties of certainexemplary useful lower temperature braze alloys.

TABLE 2 Examples of Useful Lower Temperature Braze Alloys Shear SolidusStrength Liquidus (De- Melting (pounds Composition (Degrees grees Pointper (weight Centi- Centi- (Degrees square Braze Alloy percent) grade)grade) Centigrade) inch) Easy Flo 45 45% Ag 620 605 605 8,191 15% Cu 16%Zn 24 Cd Braze 560 56% Ag 650 620 620 11,196 22% Cu 17% Zn 5% Sn

Referring to FIG. 6, there is shown a cross-sectional view of a cuttingtool generally designated as 76. The cutting tool 76 has a cutting toolbody 78 that contains a pocket 80. A PcBN blank 82 is brazed into thepocket 82 using a braze alloy so as to form a braze joint 84 between thePcBN blank and the surface that defines the pocket 80. The PcBN blank 82comprises a single piece of polycrystalline cubic boron nitride. This isin contrast to a PcBN blank that has a layer of polycrystalline cubicboron nitride on a support. PcBN blank 82 has a rake surface 85 and aflank surface 86. The rake surface 85 and the flank surface 86 intersectto form a cutting edge 87.

Referring to FIG. 7 there is shown a grooving tool 90 that has a PcBNblank 92 brazed to the body of the tool using a braze alloy. Thegrooving tool 90 is a TOP NOTCH® geometry wherein TOP NOTCH® is aregistered trademark of Kennametal Inc. of Latrobe, Pa. USA.

Referring to FIG. 8 there is shown a threading tool 96 that has a PcBNblank 98 brazed to the body of the tool using a braze alloy. Thethreading tool 96 is a TOP NOTCH® geometry wherein TOP NOTCH® is aregistered trademark of Kennametal Inc. of Latrobe, Pa. USA.

One specific method of threading that has provided excellent resultswhen using these cutting tools (i.e., threading tools) is a constantvolume threading method. In this method, the depth of the pass isconstantly decreased so that the volume of material removed from theworkpiece is constant for each pass. To achieve this constant volume onetakes the infeed per pass formula: accumulated depth=initial depth ofcut (doc)•(No. pass)^(1/2) to arrive at the depth of cut for each pass.The Table 3 below sets forth an example of this method showing the firstfour passes. Additional passes determined per the calculation arenecessary to obtain an external thread depth of 0.0789 inches.

TABLE 3 Sample Calculations for a Constant Volume Threading Method [8pitch external thread has a depth of .0789 inches] Infeed depth of cutPass No. First Calculation Second Calculation for the pass 1 25% of.0798 = .0197 NA .0197 2 .0197 · 2^(1/2) = .0278 .0278 − .0197 = .0082.0082 3 .0197 · 3^(1/2) = .0341 .0341 − .0278 = .0063 .0063 4  0197 ·4^(1/2) = .0394 .0394 − .0341 = .0053 .0053The constant volume method can be described as a method of removingmaterial in a threading operation from a workpiece comprising a ferrousalloy having a hardness between about 50 Rockwell C and about 65Rockwell C using an uncoated cutting tool. The method has the followingsteps: providing an uncoated cutting tool having body containing apocket where a superhard blank is brazed using a braze alloy into thepocket to form a braze joint wherein the braze alloy having a liquidustemperature of at least about 900 degrees Centigrade wherein the brazealloy is selected from the group comprising a nickel-gold braze alloycontaining nickel and gold, a copper-gold braze alloy containing copperand gold, a gold-copper-nickel braze alloy contains gold and copper andnickel, a silver-titanium-copper braze alloy containing silver andtitanium and copper, and a silver-palladium braze alloy containingsilver and palladium; and engaging the workpiece with the uncoatedcutting tool on multiple passes wherein each pass removes a volume ofmaterial that is substantially equal to the volume of material removedfrom the workpiece in the previous pass.

While the constant volume threading method is the preferred method ofthreading, applicants contemplate that one or more threading passes mayremove either a lower volume of material than calculated per the formulaor a lower volume of material than removed in the previous pass. Thus,such a method includes the step of engaging the workpiece with theuncoated cutting tool on multiple passes wherein each pass removes avolume of material substantially equal to or less than the volume ofmaterial removed from the workpiece in the previous pass.

Applicants note that there is a United States Patent Application by thesame inventors filed on the same day as this patent application andentitled COATED CUTTING TOOL USING BRAZED-IN SUPERHARD BLANK.

All patents, patent applications, articles and other documentsidentified herein are hereby incorporated by reference herein. Otherembodiments of the invention may be apparent to those skilled in the artfrom a consideration of the specification or the practice of theinvention disclosed herein. It is intended that the specification andany examples set forth herein be considered as illustrative only, withthe true spirit and scope of the invention being indicated by thefollowing claims.

1. A method of removing material in a threading operation from aworkpiece comprising a ferrous alloy having a hardness between about 50Rockwell C and about 65 Rockwell C using an uncoated cutting tool, theprocess comprising: providing an uncoated cutting tool having bodycontaining a pocket where a superhard blank is brazed using a brazealloy into the pocket to form a braze joint wherein the braze alloyhaving a liquidus temperature of at least about 900 degrees Centigradewherein the braze alloy is selected from the group comprising anickel-gold braze alloy containing nickel and gold, a copper-gold brazealloy containing copper and gold, a gold-copper-nickel braze alloycontains gold and copper and nickel, a silver-titanium-copper brazealloy containing silver and titanium and copper, and a silver-palladiumbraze alloy containing silver and palladium; and engaging the workpiecewith the uncoated cutting tool on multiple passes wherein each passremoves a volume of material substantially equal to or less than thevolume of material removed from the workpiece in the previous pass. 2.The method of claim 1 wherein the engaging step comprises engaging theworkpiece with the uncoated cutting tool on multiple passes wherein eachpass removes a volume of material substantially equal to the volume ofmaterial removed from the workpiece in the previous pass.